1. Field of the Invention
The present invention relates to the formation of capacitor of memory cell, and more particularly for using silicon oxide on a silicon substrate layer of silicon wafer for semiconductor device.
2. Description of the Prior Art
Currently, one of the main art for improving DRAM performance could be hemi-spherical grain (HSG) process. In fact, recently Hemi-Spherical Grain (HSG) process is gradually applied to the production technology of High-Density DRAM in practical. Furthermore, HSG process ideally will increase the surface area of silicon layer in order to expand the capacity of DRAM, this issue was presented by some of previous laboratory experience already.
Basically HSG process is firstly to be deposited an alpha-type silicon thin film on the substrate of silicon wafer inside a PCVD furnace at 1 torr and 510.degree. C. to 550.degree. C. Consequentially alpha-Silicon film surface is cleaned using SC-1 wet cleaning and then the native oxide layer is removed by HF dipping. Afterward HSG will grew up in furnace chamber. Firstly, the chamber is pre-heat before loading the wafer into furnace chamber. When wafer is irradiated about 60 seconds, then conducting gas into the chamber. At this step, temperature is arrived about 200.degree. C. to 300.degree. C., then the gas is ceased after about 60 seconds. Thirdly temperature is held at 600.degree. C. The whole treatment time is about 300 seconds at least. The pressure is about 10.sup.-5 torr when conducting the gas. Also, when the gas is not conducted into the chamber, the pressure will be about 10.sup.-8 torrs, also the gas fluid is about 10 sccms.
However, unfortunately hemispherical grain (HSG) process is still not totally desirable because there still is a short road problem, such as FIG. 1. From FIG. 1, it is apparently found that HSG in Portion 1 and HSG in portion 2 are too close so that it will cause bridging problem. On the other hand, it is still necessary to be refined again. According to this consideration, this present invention now submits a brand new preferred method for forming HSG in DRAM structure.
Generally, demand for high-density dynamic random access memory (DRAM) has rapidly increased due to widespread use of electronic equipment. In particular, the increasing popularity of some electronic equipment such as, for example, many kinds of computers are gradually increasing the demand for the large or very large semiconductor memories in this modern century and next coming twenty-one century. Therefore, the advanced manufacture technology for improvement fabrication of DRAM should be urgently need than before.